1. Field of the Invention
The present invention relates to reactive silica, a process for manufacturing the same, and use of the same. More particularly, the present invention relates to reactive silica particles which can provide a curable composition with superior storage stability and capability of producing a coating film on the surfaces of substrates, such as plastics, metals, wood, papers, glasses, slates, or the like. The coating film exhibits excellent characteristics, such as scratch resistance, weather resistance, adhesiveness, and curability. The film can be made to satisfy a wide spectrum of performances from transparent to semi-transparent, and from a glossy surface to a frosty surface. The film can for example be applied to the surface of molded articles made from polymers, such as polycarbonate, polymethacrylate, polyvinyl chloride, polyester or polyolefins, to protect the surface from scratch and contamination. The composition can be used as a material for plastic optical parts and touch panels, film-type liquid crystal elements, hard coatings of plastic molded articles, a photocurable adhesive, a photocurable sealing material, a contamination-proof or scratch-proof coating for building interior materials, a flooring material, a material for walls, or a binder for printing ink.
2. Prior Art
In recent years there is a demand for a material which can be used to make for example coatings that are excellent in characteristics, such as scratch resistance, weather resistance, adhesiveness, and curability, and which can be controlled with respect to the optical characteristics in a wide range from transparent to semi-transparent. Various coating compositions containing colloidal silica have been proposed with an object of improving the scratch resistance of the cured coatings. For example, U.S. Pat Nos. 3,451,838 and 2,404,457 disclose a thermoset coating composition containing an alkoxysilane hydrolyzate and colloidal silica as major components. Japanese Patent Publication (kokoku) No. 21815/1987 discloses a photocurable coating composition containing colloidal silica particles, of which the surface is modified with methacryloxy silane, and acrylate. In these compositions, the surface of silica particles is treated with a specific organic silane compound or under specific conditions to improve their characteristics as a coating material.
These coating materials, however, are not able to meet all the required properties such as constantly producing films which exhibit excellent scratch resistance, weather resistance, adhesiveness, and curability, and furthermore can be formulated to satisfy a wide spectrum of performances from transparency to semi-transparency, and to provide a glossy surface as well as a frosty surface.
In addition, the thermoset coating compositions disclosed, for example, by U.S. Pat. Nos. 3,451,838 and 2,404,357 require a heat treatment at high temperatures for a long time and, therefore, cannot be applied to low heat resistent plastic materials.